How do you solve y=1/2x^2-4, y=3x+4 using substitution?

1 Answer
Feb 4, 2017

Simply substitute the second equation into the first (both are solved for y already).

3x + 4= 1/2x^2 - 4

Multiply by a factor of 2 so that all terms are integers.

6x + 8 = x^2 - 8

0 = x^2 - 6x - 16

0 = (x - 8)(x+ 2)

x = 8 and -2

This will mean that y = 3(8) + 4 = 28 and y = 3(-2) + 4 = -2

Therefore, the intersection points are (8, 28) and (-2, -2).

Hopefully this helps!